Liquefied natural gas fractionation - using part of gas as cooling medium allowing temp. regulation using one fractionation column

摘要

In batch fractionation of LNG, the rising vapour is condensed by other part of LNG vapour to obtain low boiling component consisting of gaseous methane obtd. in a fractional condenser and a high boiling component contg. a large amt. of high boiling fraction having higher b.pt. than ethane. Low boiling component consisting essentially of methane and uncondensed fraction of LNG is collected and converted completely to gaseous form to obtain LNG, and fraction contg. higher boiling fraction than ethane is totally condensed by cooling with part of LNG, to obtain mixt. of gaseous medium. Since part of LNG is used as coolant and no other cooling medium is necessary, regulation of heating temp. is performed in one fractionation column, and installation cost is reduced. Cold is recovered by executing a Rankin cycle using mixt. of the medium.